1. Field of the Invention
The present invention generally relates to breast implants, and more specifically relates to breast implants having drug-eluting membranes incorporated therein for diffusing therapeutic solutions, such as antibiotic solutions, into surrounding tissue to minimize the chances of infection, rejection, and/or post-implantation complications.
2. Description of the Related Art
Implantable prostheses are commonly used to replace or augment body tissue. In the case of the female breast, it sometimes necessary to remove some or all of the mammary gland and surrounding tissue in order to treat breast cancer. This surgery leaves a void that can be filled with an implantable prosthesis that supports surrounding tissue and maintains the appearance of the body. The restoration of the normal appearance of the body has an extremely beneficial psychological effect on post-operative patients, eliminating much of the shock and depression that often follows extensive surgical procedures. Implantable mammary prostheses are also used for enlargement of the breast, commonly referred to as breast augmentation.
Implantable mammary prostheses, commonly referred to as breast implants, are usually formed of a silicone polymer shell and are filled with saline or silicone gel. Such implants generally have a substantially flat posterior face that is positioned against a patient's chest and a domed anterior face. It is often desirable for a perimeter region of the implant, i.e., the region where the anterior and posterior faces meet, to have a relatively small radius of curvature, particularly at the upper end of the implant. A relatively small radius of curvature in the transition between the anterior face and the posterior face in the upper pole region of the prosthesis is desirable because it permits a relatively smooth transition between the mammary tissue and the implant when the prosthesis is implanted. However, a small radius is sometimes associated with the appearance of creases that extend inward from the perimeter of the prosthesis, which is commonly referred to as “scalloping.” Scalloping tends to occur when the prosthesis is filled with fluid and the patient is upright such that the weight of the filling material is pulling downward on the prosthesis. The creases often appear on the anterior face of the prosthesis, which can be aesthetically undesirable as the creases can sometimes be discerned through the overlying skin of the patient.
Breast implants are typically manufactured by dipping an appropriately sized and shaped mandrel in a biocompatible elastomer such as silicone. In one common procedure, the mandrel is dipped into a silicone dispersion and then removed to allow partial cure or solvent evaporation. The dipping and curing process is generally repeated several times. Once the shell has been formed it is removed from the mandrel. The dip-molding process results in the formation of an implant shell that has an opening, e.g., a circular hole (mandrel hole) in one of its faces. The mandrel hole is subsequently covered with a patch that seals the hole, thus forming a complete, fluid impervious shell. The patch is attached to the implant shell using silicone rubber or other similar biocompatible adhesive. The patched shell is sometimes provided with a fill port or valve extending through a face of the prosthesis. The completed shell can either remain unfilled, be pre-filled, or intraoperatively filled through the small fill port or valve with saline, gel, foam, or combinations of these materials. The fill port or valve is sealed or closed, and the implant is sterilized.
After implantation, breast implants are subject to complications from infection. A breast implant infection may manifest itself with clinical symptoms, or there may be no outwardly noticeable symptoms. When a breast implant infection becomes established, a bacterial biofilm typically forms around or in areas of the implant surface. The biofilm, a proteoglycan polysaccharide produced by the bacteria, protects the bacteria from being affected by even high concentrations of antibiotics. Thus, once the infection takes hold, conventional concentrations of systemic antibiotics cannot eliminate the infection but can only keep it from spreading further. Thus, a chronic subclinical inflammatory situation develops, which may lead to eventual implant rejection.
Symptomatic infections usually result in the removal of the implant. Non-symptomatic infections (i.e. sub-clinical) may lead to chronic inflammatory responses that can be a major cause of collagen capsular contracture. Capsular contracture is one of the major drawbacks of breast augmentation and reconstruction using silicone implants.
In view of the foregoing, there is a need for breast implants, breast implant systems and surgical techniques that can reduce or eliminate infection and the resulting capsular contracture. Such an implant would represent a major improvement in breast implant performance and patient satisfaction.